Process for making pyrosulphuryl chloride



March l2, 1946. y N. A. LAURY ETAL 2,396,581

PROCESS FOR MAKING PYROSULPHURYL CHLORIDE Filed Feb. 2, 1945 Patented Mar. 12, 1946 UNITED STATES .PATENT 4OFFICE PROCESS FOR Napoleon Arthur Laury, Boniface Lombardo, S

MAmNG PimosULPmmrL cnLonmE Bound Brook, and Joseph omerville, N. J

., assignors to America-n Cyanamid Company, New York, N. Y., a corporation of Maine Application February 2. 1945, Serial No. 575,820 8 Claims.l (Cl. 23-203) This invention relates to an improved process of preparing pyrosulphuryl chloride.

Pyrosulphuryl manufacture. One of these processes involved the reaction of fuming sulphuric acid with sulphur monochloride. The reaction, while practicable, is expensive, as

and has to be freed bycareful fractional distillation. y

Various authors have suggested the reaction of sulphuric acid anhydride itself monochloride.

of sulphuric chloride.

The reaction between the S03 and xonochloride is not particularly critical. be effected under atmospheric pressure the sulphur If it is cooling is needed at the beginning, as serious'losses of reactants may take place above 35 C.

sure vessels is not economically justified. In

either case, however, high yields of or more result from the reaction.

It is an advantage o1' the process of the present ntion that no serious corrosion problem is resistant material is necessary.

The invention will be.described in greater de- Eample 1 A heated steel still is continuously fed with 30% oleum at such a rate that the temperature of the liquid in the still is not over 200 C. and the overflow from the still contains 4% a steam coil to 'I'he temperature at a point where In no case shfmlf' some heat is applied by means of drive out the remaining SO2.

is permitted to rise but is kept the loss of S03 is negligible.

the temperature exceed 60 C. Water maybe circulated in this` steam coil to restrain the reaction if necessary early in the charge. The charge is steel still. From this still the first runnings contain some S03; so this condensate is run to a reaction tank to be used in a succeeding charge. The main fraction distilled is pure. A packed column is used on this still but it is merely a safeguard in case there may be some unreacted SzClz. Normally the quantities of reactants can be so regulated that no residue is left in the still at all.

The reaction is preferably made semi-continuous,v as is shown on the/flow sheet, by using two reaction. tanks, in one of which the reaction is proceeding by feeding sulphur monochloride the ilow sheet, being heated to complete the reaction and drive off S02, followed by withdrawing. the charge and introducing it to the product still which removes S03 and distills over the pure pyrosulphuryl chloride. As soon as the charge has been removed a fresh charge of S03 is run in and then sulphur monochloride is introduced with cooling while the charge in the other vessel is heated to drive of! SO-i, and the charge then led to the product still. The product still operates continuously or semi-continuously and high output is obtained with a minimum of supervision, as the temperatures and .reaction times are not critical.

Example 2` Liquid S03, substantially free of H.SO4l is produced by distillation as described in Example 1. A charge of it is run into a closed steel pressure tank. Then a quantity of sulphur chloride is charged into the tank by pumping or other suitable means. The quantity used should be equivalent to a ratio of one mol of SzCla to ve mois of S03 plus an excess of 5 to 15% of the latter. Using temperature and pressure instruments as guides, the charge is heated, preferably with a steam coil, so that the readings rise gradually to '15 C. and 165 pounds over a period of one hour or longer, according to the size of the charge.

The tank now contains pyrosulphuryl chloride, S02 and rsome unreacted S03, the latter two as These gases are released to a scrubbing S03 is condensed to' a liquid by cooling and then transferred to storage still under pressure. pure enough as it is for most purposes but a distillation to free it of some dissolved gas and traces of unreacted SzClz is necessary to reach high purity. The yields both of pyrosulphuryl chloride and liquid SO2 approximate 90%.

The use of a pressure vessel has been described in conjunction with the batch process. It is, of course, possible to incorporate pressure vessels in the semi-continuous ilow sheet described in connection with Example 1, and where large production is desired this might since the BO: set free in the reaction remains in the pressure vessel until the reaction has been completed, the SO: scrubber is operated intermittently.

The term sulphur trioxide" has been used in its general sense as covering oxides o! sulphur having 3 atoms of oxygen for every atom of sulphur,and which may be considered as anhydrides of sulphuric acid. The term is not to be restricted to the monomer S03 only but includes polymers such as 820s o r S309 which may be present in the liquid. 0f course, polymers are unsuitable if they are present in such amount that the prodliquid at the reaction temperature. so high that the mass solidies the process practical. In the claims, the term oxide will be used in the above general sense.

We claim:

1. A method of preparing pyrosulphuryl chloride which comprises reacting liquid sulphur trioxide, substantially free from sulphuric acid, with sulphur monochloride until the reaction is cornplete, and removing sulphur dioxide formed.

2. A method of preparing pyrosulphuryl chloride which comprises reacting liquid sulphur trioxide, substantially free from sulphuric acid, with sulphur monochloride until the reaction is complete,removing sulphur dioxide formed and purifying the pyrosulphuryl chloride by distillation and condensation at a temperature at which pyrosulphuryl chloride is condensed and sulphur trioxide remains in the gaseous form.

3. A method according to claim 1, in which the reaction proceeds by introducing sulphur monochloride into liquid sulphur trioxide.

4. A method according to claim 2, in which the reaction proceeds by introducing sulphur monochloride into liquid sulphur trioxide.

5. A method according to claim 1 in which the reaction is effected in a closed vessel under pressure.

6. A method according to claim 2 in which the reaction is effected in a closed vessel under presin which sulphur monochloride is introduced into liquid sulphur trioxide at a temperature not C. until all of the introduced and the reaction and completing the reaction at a higher temperature not in excess of 60 C.

8. A method according to claim 2 in which sulphur monoclloride is introduced into liquid sulphur trioxide at a temperature not exceeding 35 C. until all of the sulphur monochloride has been introduced andv the reaction has slowed down. and completing the reaction at a higher temperature not in excess of 60 C.

NAPOLEON ARTHUR LAURY.l JOSEPH BONIFACE LOMBARDO.

be advantageous.y 

